34 NKW UNIONIDil<: OV THE 



(nobis,) but is more oval. The posterior lobe of the cardinal tooth ol" the left valve is 

 disposed to be divided, almost making it tripartite. 



Unio obnubilus. pi. 17, fig. 64. 



Testa Isevi, elliptica, suboompressa, posticiJ subbiaDgulata, injequilaterali ; valvulis subcrassis ; natibus pro- 

 minulis, ad apices undulatis; epidermide tenebroso-fusca, eradiata, subnitens; dentibus eardinalibus 

 subgrandibu.=, subpyramidatis, crenulatis, in utroquc valvule duplicibus ; lateralibus longis, lamellatis 

 curvisque ; margarita purpurea et irideseente. 



Shell smooth, elliptical, somewhat compressed, subbiangular behind, inequilateral ; 

 valves somewhat thick ; beaks a little prominent and undulate at the tip ; epidermis 

 dark brown, without rays and somewhat shining ; cardinal teeth rather large, rather 

 pyramidal, crenulate, double in both valves; lateral teeth long, lamellar and curved; 

 nacre purple and iridescent. 



Proc. Acad. Nat. Sci., 1857, p 169. 



Eah. — Buckhead Creek, Burke Co., Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. -9, Length 1-5, Breadth 2-G inches. 



Shell smooth, elliptical, somewhat compressed, somewhat biangular behind and 

 rounded before ; substance of the shell somewhat thick, very slightly thicker before ; 

 beaks a little prominent, and placed towards the anterior margin, with numerous, 

 somewhat irregular concentric undulations at the tip; ligament rather long and 

 rather thin ; epidermis dark brown, without rays, shining on the umbones, with rather 

 distant marks of growth ; umbonial slope somewhat raised and subangular ; cardinal 

 teeth rather large, rather pyramidal, crenulate and double in both valves ; lateral 

 teeth long, lamellar and curved, the lower division being usually much the larger ; 

 anterior cicatrices distinct, rather large and well impressed ; posterior cicatrices large 

 and confluent ; dorsal cicatrices placed in the centre of the cavity of the beaks ; 

 cavity of the shell rather shallow and wide ; cavity of the beaks shallow and rounded; 

 nacre purple and iridescent. 



So/i Paris. — Branchial uterus . No ova in the branchial ovisacks, Ijut imma- 

 ture ones were found in the ovarium. BrancMce large, thin, nearly semicircular, rather 

 oblique posteriorly, inner ones very much the larger, free more than half the length 

 of abdominal sack. Palpi small, thin, subtriangular, united only at the upper por- 

 tion of the posterior edges. Mantle thin, slightly thickened at the margin, being 

 slightly colored at the edges, and crenulate below the branchial opening. Branckial 

 opening rather large, with small, very dark brown papillas on the inner edges. Anal 

 opening very large, with numerous very small dark brown papillae on the inner 

 edges. Super-anal opening rather long, slightly colored on the inner edges and 

 united for a short distance below. Color of the mass whitish. 



Remarks. — A number of specimens of this species were received from Bishop Elliolt 



